Herbert Spencer (1820-1903) was a British social philosopher, and is often regarded as one of the first sociologists.

His early influences included the utilitarian philosophy of Jeremy Bentham and an early theory of evolution developed by the French naturalist Jean Baptiste Lamarck.

In 1851 Spencer published Social Statics, a work in which he stressed the importance of individual freedom and the inevitability of human progress. In Principles of Psychology (1855) Spencer sed that all organic matter originates in a unified state and that individual characteristics gradually develop through evolution. The evolutionary progression from simple to more complex and diverse states was an important theme in many of Spencer's later works. In A System of Synthetic Philosophy (1860) Spencer outlined his plan for a comprehensive system of philosophy, based on evolution, that would integrate all existing fields of knowledge. The initial installment in this project, First Principles, appeared in 1862. Later works in the series include Principles of Biology (2 volumes, 1864-1867), Principles of Sociology (3 volumes, 1876-1896), and Principles of Ethics (2 volumes, 1892-1893).

After Charles Darwin published On the Origin of Species in 1859, Spencer acepted Darwin's theory of natural selection. Spencer was an influential proponent of Social Darwinism, which attempted to apply Darwin's theory to human societies.

Spencer coined the phrase "survival of the fittest" to describe the competition among individuals and groups of humans. He argued that human progress resulted from the triumph of more advanced individuals and cultures over their inferior competitors. Wealth and power were seen as signs of inherent "fitness," while poverty was seen as evidence of natural inferiority. When social Darwinist ideas were debunked in the early 20th century, Spencer's reputation as a philosopher and social theorist declined.